Crystallographic Texture Variation Research Articles

Effects of local processing parameters on microstructure, texture, and mechanical properties of electron beam powder bed fusion manufactured Ti–6Al–4V

Electron beam powder bed fusion scan strategies for parts or part groupings of various sizes and scan line lengths have been found to inadvertently lead to significant variations in crystallographic texture and mechanical properties for Ti–6Al–4V. This occurs over a range of scan line length that is well below the maximum scan line length recommended by the electron-beam powder bed fusion machine manufacturer. The microstructural attributes such as α lath thickness, prior β grain size, and β phase fraction were similar for materials fabricated under short and long scan line length conditions, but the crystallographic textures varied considerably. Electron backscatter diffraction measurements indicate the basal pole [0001]α was strongly aligned with the build direction for long scan line length conditions, whereas 112‾0α were aligned with the build direction for short scan line length conditions. Subsequent prior β reconstructions indicate a preference for alignment of 110β and 100β with build direction for long and short scan line length conditions, respectively. Both yield and ultimate tensile strengths along the build direction were approximately 8% higher for long scan line lengths, consistent with the observed differences in texture. The impact of a sub-solvus hot isostatic pressing was also investigated, however, this did not significantly change the textures of as-built materials or the relative strengths for the two processing conditions.

Texture mapping in electron beam welded dissimilar copper-stainless steel joints by neutron diffraction

In this study, the crystallographic texture variation of electron beam welded dissimilar copper to 304L stainless-steel joints was investigated using Time-of-flight neutron diffraction measurements. The effect of beam oscillation by changing its oscillation diameter on texture orientation variation was evaluated. Neutron diffraction measurements were performed using General Materials Diffractometer beamline at Rutherford Appleton Laboratory neutron radiation source. Phase fractions and variations of crystallographic texture in terms of pole figures and inverse pole figures were obtained. The stronger texture we found in all regions of the joints i.e. heat-affected zone and fusion zone for oscillating beam compared to its non-oscillating counterparts. Also, by increasing the oscillation diameter, from its optimum value, a weaker texture was found, which had a detrimental effect on mechanical properties. Electron-backscatter diffraction texture measurements were also performed to compare and complement the results obtained from neutron texture.

The Effect of a Substrate Material on Composition Gradients of Fe-Ni Films obtained by Electrodeposition

The electrodeposition of FeNi alloy films was performed galvanostatically in the sulfate solution (Fe2+/Ni2+ mass ratio 1:2) in order investigate their co-deposition mechanism. The FeNi layers were deposited at variable substrates (copper, brass, silver) under the same chemical (electrolyte composition) and electric plating (current density value) conditions. After applying various time, substrates and external magnetic field orientation, the quality of the obtained film was examined. The surface morphology and crystallographic texture variation were investigated by the Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Wavelength Dispersive X-ray Fluorescence (WDXRF) and Laser Confocal Scanning Microscope (LCSM). The anomalous co-deposition of iron group metals is evidently dependent on the substrate.

Crystallographic texture evolution and tribological behavior of machined surface layer in orthogonal cutting of Ti-6Al-4V alloy

The machining-induced crystallographic orientation variation in the plastic deformation layer on the mesoscopic scale usually occurs when severe plastic deformation undergoes in the machined surface layer, which will further affect the macroscopic mechanical performance of the machined parts. The orthogonal cutting experiments of Ti-6Al-4 V titanium alloy were carried out to confirm the effectiveness and reliability of the established finite element method (FEM) simulation cutting model with ABAQUS. From the perspective of macroscopic deformation, the shear strain and strain rate history were obtained, and this provided the fundamental data to simulate the machining-induced surface crystallographic texture evolution process using a visco-plastic self-consistent (VPSC) code. The pole figures and orientation distribution function (ODF) maps of crystallographic texture were produced and analyzed using a toolbox of Matlab. In order to validate the existence of crystallographic texture orientation with anisotropy, friction and wear tests were performed to explore the influence of crystallographic texture variation on the macroscopic properties of machined surface. The difference of friction coefficients and wear track width in the cutting direction and vertical cutting direction confirmed the hypothesis, and the machining-induced crystallographic texture evolution will alter the surface integrity and eventually the mechanical behavior of machined parts.

Characterization of grain structure and crystallographic texture variation during the production of a Properzi semi-product

The solidification on the casting wheel is the first step of the Properzi process which is followed by rolling in several steps, in this case 11 rolling steps. The uniqueness of the technology is that the rolling occurs from 3 directions. Therefore, a completely unique texture develops in the product compared to classic rolling. This aluminium semi-product is the base product for wire drawing. The characteristic of the strand greatly influences the success of the wire drawing therefore, knowing the crystallographic texture is demanded. In this paper, the grain structure and crystallographic texture variation during the full production technology of a Properzi semi-product is characterised. The examined strand includes all the technological steps of the process (casting and the 11 rolling steps). To perform such investigation, strand the complete production must be stopped for sampling because of the closed and semi-continuous type of the process, Therefore, the presented work is unique. To characterize the semi-product, cross-sectional and longitudinal-sectional samples were prepared. Grain structure and X-ray diffraction (XRD) texture examinations were carried out on the two sample series. Based on the results it can be stated, that despite of the grain refinement, initially a columnar structure formed and a strong <100> texture developed. During rolling, the <111> fibre texture developed. After the last step, the initial <100> texture is still present besides the <111> fibre texture. Consequently, the initial conditions of the crystallization highly determine the developed texture of the semi-product.

Quantifying Crystallographic Texture Variation in a Titanium Billet

Ti-834 and other titanium alloy forgings can contain regions of similarly orientated primary alpha grains called macrozones that can have a deleterious effect on performance in-service. Understanding the origin of macrozones and how they change during processing is an important step in optimising process routes for these alloys. In this work a detailed characterisation of crystallographic texture variation was carried out on the cross-section of a 250 mm diameter Ti-834 billet using optical metallography, EBSD and neutron texture analysis. Results showed there was a variation in texture and macrozone size and shape through the billet with each macrozone composed of a single hcp component, with varying degrees of orientation spread. The texture of the majority of macrozones can be classed as either axial (c-axis parallel to the billet axis) or transverse (c-axis perpendicular to the billet axis). In the centre of the billet cross-section, the global texture was dominated by a fibre-like {10 1 0} texture due to a dominance of transverse macrozones. At the edge, there was a greater proportion of axial macrozones which gave rise to an additional {0002} component.

Hot Rectangular Extrusion Textures of Six Mg‐Alloys Via Neutron Diffraction

Due to the high quality and statistics utilizing neutron diffraction for texture analyses, the crystallographic texture variation of six Mg‐alloys is described in detail (AM20–AZ31–AZ61–AZ91–ZC71–WE43). More or less in all cases, the crystallographic texture is composed of some ideal texture components such as {0001} &lt;10–10&gt; and {10–10} &lt;11–20&gt; and fiber components such as &lt;0001&gt; // ND and &lt;10–10&gt; // ED. There is a dependency of the existence and texture sharpness of texture components with alloying elements such as the amount of Al. ZC71 is special with one dominating texture component {10–10} &lt;11–20&gt;. WE43 shows the split of the central pole in the basal pole figure but texture components are identical to other alloys without the tilt.

The Initiation and Propagation of Dynamic Abnormal Grain Growth in Molybdenum

Plastic straining can initiate and propagate abnormal grains at temperatures significantly lower than is possible by static annealing. This phenomenon is termed dynamic abnormal grain growth (DAGG). Experiments that produce DAGG in commercial-purity molybdenum sheet materials are used to study the initiation and propagation of abnormal grains by plastic straining at temperatures from 1673 K to 2073 K (1400 $$^\circ $$ C to 1800 $$^\circ $$ C). The minimum strain necessary to initiate DAGG, termed the critical strain, decreases approximately linearly with increasing temperature. The variation in critical strain values observed at a single temperature and strain rate is well described by a normal distribution. An increased fraction of grains aligned with the $$\left\langle 110\right\rangle $$ along the tensile axis, a preferred orientation for DAGG grains, appears to decrease the critical strain for DAGG initiation. DAGG grains preferentially grow into the finest-grained polycrystalline regions, which suggests that the driving force for DAGG propagation is primarily from grain-boundary curvature. No effects of local crystallographic texture variation on growth are evident in microstructures containing DAGG grains. Together, these observations support the hypothesis that plastic straining during DAGG acts primarily to increase boundary mobility, rather than to increase the driving force for boundary migration.

Influence of dosing sequence and film thickness on structure and resistivity of Al-ZnO films grown by atomic layer deposition

Aluminum-doped zinc oxide (AZO) films were deposited onto amorphous silica substrates using an atomic layer deposition process with diethyl zinc (DEZ), trimethyl aluminum (TMA), and deionized water at 200 °C. Three different Al doping sequences were used at a ZnO:Al ratio of 11:1 within the films. A minimum film resistivity of 1.6 × 10−3 Ω cm was produced using sequential dosing of DEZ, TMA, DEZ, followed by H2O for the Al doping step. This “ZAZW” sequence yielded an AZO film resistivity that is independent of film thickness, crystallographic texture, and grain size, as determined by high resolution x-ray diffraction (XRD). A pseudo-Voigt analysis method yields values for grain sizes that are smaller than those calculated using other XRD methods. Anisotropic grain sizes or variations in crystallographic texture have minimal influence on film resistivity, which suggests that factors other than film texture, such as intragrain scattering, may be important in influencing film resistivity.

Through-thickness texture profiling by energy dispersive synchrotron diffraction

Two new approaches that make use of the advantages of energy dispersive diffraction were applied to investigate through-thickness variations of the crystallographic texture: the `real-space' and the `Laplace-space' methods. The first consists of defining a small gauge volume by adding a pair of slits in the primary and the diffracted beams. Thus the depth resolution is achieved by a decoupledztranslation of the gauge through the sample. The second method is based on the Beer attenuation law, and the depth resolution is achieved by assigning pole figures of different order reflections (e.g.0002, 0004…) to different average information depths. Wrought rolled AZ31 magnesium alloy was selected as a `model' material for the experiments because of the low X-ray absorption of Mg. The through-thickness crystallographic texture variation was generated by sample bending. The results give a first insight into the possibilities of fast texture depth profile investigation applying nondestructive methods and represent a step forward towards a simultaneous evaluation of residual stress and texture gradients.

Microtexture and anisotropy in wire drawn copper

In many processing operations, it is critical to know the relationship between the resultant sample geometry and the distribution of crystallographic or grain orientations within the polycrystalline aggregates. The spatial variations in crystallographic texture associated with different parts of the sample geometry can influence differences in the plastic response within different regions of a sample. In this paper we present a study of such local variations in the texture (microtexture) as well as grain boundary or mesotexture associated with copper wire and its implications for micromechanical inhomogeneity within a sample volume. The unique experimental and analytical aspects of such microtexture characterization are discussed along with the issues of grain boundary structural parameters and its role in microtexture and anisotropy. The presence of differences in twin frequency in different regions of the sample is suggested as a possible source of strength anisotropy.

Crystallographic anisotropy in thin film magnetic recording media analyzed with x-ray diffraction

The crystallographic anisotropy of CoCr alloy films deposited on a Cr underlayer was investigated with grazing incidence x-ray scattering (GIXS). The effect of circumferential mechanical texturing of the NiP substrate (producing microgrooves through polishing) was explored. The Co was found to grow heteroepitaxially on the Cr underlayer with the Co(112̄0) growth planes parallel to the Cr(001) growth planes. We observe no significant differences in Co lattice parameter in the circumferential and radial directions, although we do see variations in crystallographic texture between these two directions. From GIXS peak intensities, we observe that there is a greater population of crystallites with their c axis pointed along the grooves. This analysis was done after allowing for the effect of the varying local surface normal due to the substrate grooves. The ratio of the coercivities in the two directions scales with the ratios of the c-axis population densities. Two simple quantitative models of the magnetic properties of the aggregate have been constructed: strongly coupled grains and uncoupled grains. The predictions of these models are compared to the observed properties.

Delayed hydride cracking behavior for ZIRCALOY-2 tubing

The delayed hydride cracking (DHC) behavior for ZIRCALOY-2 tubing was characterized at temperatures ranging from 93 °C to 288 °C. Testing was performed on the three types of pressure tubes that were used in the construction of the Hanford N Reactor, Richland, WA. A two-stage cracking response was observed for all tube types, with a very high K sensitivity in the threshold (stage I) regime followed by a region that was insensitive or moderately sensitive to the applied K level (stage II). The stage II crack velocity was a thermally activated process with an apparent activation energy of 68 kJ/mol. This energy level was consistent with the theoretical activation energy associated with hydrogen diffusion into the triaxial stress field ahead of a crack. Above a critical temperature of 180 °C, cracking occurred only when specimens were subjected to an overtemperature cycle. Below this critical temperature, DHC occurred regardless of whether specimens were heated or cooled to the test temperature. Differences in crack velocities and threshold responses for the various tube types were attributed primarily to variations in crystallo-graphic texture. Postirradiation testing revealed that irradiation to a fluence of 7.7 × 10(21) n/cm2 caused a 50-fold increase in crack growth rates. Metallographic and fractographic examinations were performed to understand operative DHC mechanisms.